This application is based on application Nos. 98-62634 and 99-55276 filed in the Korean Industrial Property Office on Dec. 31, 1998 and Dec. 6, 1999 respectively, the contents of which are incorporated hereinto by reference.
(a) Field of the Invention
The present invention relates to an alignment layer printing device, more particularly to an alignment layer printing device for liquid crystal displays wherein waste alignment liquid materials collected after the printing of alignment layers can be reused.
(b) Description of the Related Art
The response of liquid crystal to external forces such as electric fields, etc. varies since their physical constants depend on the state of their molecular alignment. Therefore, liquid crystal molecular alignment control is an essential technology in display component construction as well as in liquid crystal physical property research. However, it is difficult to obtain a uniform molecular alignment simply by filling the gap between glass substrate plates with liquid crystal material. Therefore, it is common to form an alignment layer on the glass substrate plate.
Although an alignment layer can be made mainly of inorganic materials, organic materials, or a combination of both, organic materials are mainly used as the composition material of practical liquid crystal display components.
Since the introduction of SiO vacuum deposition suggested by Janning in 1972, the characteristic properties of liquid crystal materials have not been adversely effected by either the mass production of display components or the alignment control technology for liquid crystal display components. Hence, an alignment control technology employing suitable organic polymers for mass production has developed. That is, liquid crystal molecular alignment is controlled by rubbing organic polymer layers formed on glass substrate plates by a rotational coating method or a printing coating method, and then curing.
The rubbing method has been know since Mauguin observed in 1911 that the major axes of liquid crystal molecules become evenly aligned in a rubbed direction when glass substrate plates are rubbed in a certain direction by materials such as cloth, etc. Ever since then, even though many researchers have been investigation the rubbing method for appropriate substrate plates and thin layer materials, a definite selection basis for these materials has currently not yet established.
However, because of the use of high hydrolytic Schiff base liquid crystals since the beginning of the mass production of twisted nematic type LCD components, glass frit sealing capable of securing components reliably was essential, and hence polyimide based materials which exhibited no problems in high temperature treating processes were selected. Thereafter, polyimide based materials have proved to be more superior to other organic polymers in aspects of printing, rubbing, alignment control, and chemical stabilization, so that even today polyimide based materials are widely used as alignment layer materials of various LCD components.
Generally, polyimide based polymers synthesize polyamic acids by reacting diamine and acid anhydride in a solvent, wherein the material for printing is polyamic acid that becomes polyimide through the drying, heating, and curing processes after printing.
The methods for forming an alignment layer using this polyimide include various methods such as spinning, spraying, dipping, printing methods, etc., with the printing method currently being mainly used on account of it compatibility with mass production processes.
FIG. 1 is a schematic drawing outlining an alignment layer coating device using a printing method wherein alignment layer raw material that is necessary for coating is first passed through a supplying pipe (3) from an alignment layer raw material supplying container (2) and supplied by being dropped into the gap between a rotational doctor roll (8) and an anilox roll (6) through a syringe (4). The supplied alignment layer raw material is squeezed between the two rolls (6 and 8) resulting in the formation of a uniformed liquid layer on the surface of anilox roll (6). A copper plate (10) transfers the uniformly formed liquid film received from the anilox roll (6) onto the transferred substrate plate (18) placed on the transferring plate (16).
However, only about 30% of the polyimide solution dropped on the anilox roll (6) is used in the glass substrate plate printing while the remaining 70% is pushed by the doctor roll (8) oscillating on the anilox roll (6) and dropped into a waste liquid receiver (12) at an end of the anilox roll (6). A waste liquid (14) contained in the waste liquid receiver (12) is disposed into a waste liquid tank (22) through a waste liquid tube (20).
In this manner, manufacturing costs for a conventional alignment layer printing device increase due to excessive raw material costs since about 70% of solution out of the supplied alignment layer raw material is wasted, i.e., not actually used for the alignment layer printing.
Additionally, if the waste alignment material liquid is disposed without any special treatment, it can cause contamination of the environment.
It is an object of the present invention to provide an alignment layer printing device wherein the manufacturing costs are restrained and environmental contamination can be diminished by reusing waste alignment material liquid which is not used in the alignment layer printing and disposed into a waste liquid receiver.